<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    var user = ['tom','jack'];
    user[100] = 'frank';
    console.log(user);
    for (var i in user){
        console.log(i);
        console.log(user[i]+'你好');


    }

</script>
</body>
</html>